


Soft and Warm like Mashed Potatoes

by damnedxfate



Category: Undertale (Video Game)
Genre: Alternate Universe - Swapfell (Undertale), Alternate Universe - Underfell (Undertale), Biting, Cherry Sans - Freeform, Dirty Talk, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Ecto-Tongue (Undertale), Ecto-Vagina (Undertale), M/M, Mentions of Breeding, Nipple Play, Raffle Prize, Rough Sex, Size Difference, Some Pain Play, Swapfell Papyrus (Undertale), Swapfell Sans (Undertale), Underfell Papyrus (Undertale), Underfell Sans (Undertale), ecto-breast, edgelord supreme in the background, first time with a pussy, fluffyhoodys, heat - Freeform, virgin but also not, virgin female body
Language: English
Status: Completed
Published: 2018-12-06
Updated: 2018-12-06
Packaged: 2019-09-12 15:10:24
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,169
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16875135
Author URL: https://archiveofourown.org/users/damnedxfate/pseuds/damnedxfate
Summary: Cherry's body has thrown him into a much thought lost heat. But his magic decided to give him parts he had never used before. Instead of being sensible and going to Mutt for help he hid himself away. Leaving an anxious Mutt going out of his mind in worry unaware of the truth.Until Edge appears and puts a stop to his brother's idiocy.





	Soft and Warm like Mashed Potatoes

**Author's Note:**

> This is a raffle prize for a friend on Tumblr~

It was surprising he hadn’t worn a hole into the carpet like his brother said he would. Mutt hadn’t stopped his pacing or checking his phone periodically though he knew it hadn’t rung or vibrated.   
It’s been a several days since he last heard from his boyfriend, Cherry the Underfell Sans, and their portal had gone offline.   
  
None of the others had heard anything either. Just sudden and complete radio silence. Many had gone into a panic thinking the Underfell world’s timeline had destabilized despite the machine and thrown them into a reset loop. But the scans came back clear. Meaning the Fells were still on the surface but had chosen to cut themselves off. 

 

Mutt’s entire being screamed at the discovery.

His Cherry was somewhere he couldn’t reach and had done it willingly.

 

He hadn’t slept or eaten properly since then. Even his normally stoic brother was showing  barely hiddens signs of stress. Black obviously missed Edge but was loathed to admit the weakness. That was a whole other story. Prideful fools.

 

Black was being productive at least. Still going to work and getting things done.    
Mutt was his own boss and didn’t need any permission to spend who knows how many days holed up in the house waiting for any news. Walking the same path through the hallways, down to the machine and back. 

Mutt was going out of his  stars damned mind. His poor phone was showing stress cracks from where he would grip it. Chips missing from the screen, slowly increasing in number with each desperate text for an update.   
  
He would give anything to have his Cherry back in his arms. Inhale his sweet sugar smell, feel those beautiful bones pressed against him. Mutt wanted to kiss the soft planes of Cherry’s stomach down to the apex of his thighs. Swallow down the little bright red shaft until it nestled perfectly against his tongue just barely tapping the back of his throat. Despite Cherry’s ‘shortcomings’, Mutt loved how the little cock rested so perfectly in his mouth so Mutt could savor each drop. Cherry’s thick, syrupy sweetness glazing his tongue from sexual excitement an addiction he would never kick. Mutt wanted to rub his scent all over the tiny skeleton. Re-mark him, reclaim him. 

Convince Cherry never to leave him again.   
  
His phone pinged with a notification. The sound startled him so badly he nearly dropped it before flipping it around to see. Maybe it was finally good news?!   
  
**‘Systems Alert.** **  
****Trans-dimensional Warp Drive activated.** **  
****Reading…** **  
****Location Identified.** **  
** **Underfell has connected**

**Transfering’**

 

Holy...Fucking…   
  
Mutt didn’t finish his thought. This time he didn’t drop his phone, moreso flung it in his mad dash to the basement. Underfell had connected to his machine. The portal was open and someone was coming through!   
  
“Cherry!?” Mutt yelled as soon as he made it down the stairs. Not stopping at the open door just busting it open in his haste. It wasn’t Cherry that awaited him by the still open portal but Edge, Cherry’s brother.   
  
Edge looked haggard. Like he hadn’t rested much if even at all. His normally pristine appearance was askew. The armor not quite centered showing off the body suit he wore underneath to prevent the leather and metal from chafing his bones. His boots were unbuckled and his jeans wrinkled. He was even missing his signature burgundy scarf.   
Dark shadows were burned under his eye sockets giving the illusion of heavy eye bags.    
Edge looked like the past few days had been a living hell but what mattered was that Cherry wasn’t with him.   
  


Mutt saw red.   
  
“What happened?! Where is he?! Tell me now you spiky prick or i’ll-” Mutt stomped forward to grab Edge and shake the answers out of him if he had to. He didn’t expect his hands to be caught and his body flung through the portal over Edge’s shoulder in a classic defense maneuver that Mutt would've easily broken out of if he wasn’t worried out of his mind.   
  
The suffocating pressure of the negative space between worlds pushed him down from all angles. Pulling him apart piece by piece only to slam his body back together on the other side.    
He landed in a heap on the concrete of the Fell’s basement, unforgiving and cruel. 

Mutt lay there groaning until he heard the portal over head distort. Peeking upward until his eyes met Edge’s. He had stuck his head through the portal but nothing else.   
  
“MAYBE YOU CAN TALK SOME REASON INTO HIM. I WILL BE STAYING IN YOUR WORLD WITH BLACK (probably the only reasonable Sans) YOU WILL GO UPSTAIRS AND HELP CHERRY WITH HIS PROBLEM OR SO HELP ME I WILL NEUTER YOU AND SPAY HIM!”   
  
With one last glare Edge disappeared and the machine turned off with a loud unsympathetic buzz. The nearby screen showing that the connection had been turned off. Swapfell was no longer receiving connection from Underfell. Mutt was trapped here and-   
  
Holy shit he was in Underfell, where Cherry was, and he was laying on the floor like a fucking idiot. 

Wait did Edge say ‘spay?’ whatever. He had a boyfriend who needed him if Edge’s disheveled appearance meant anything. A mate who was upstairs and they were alone until the portal opened up again. What ever ‘help’ Cherry needed he was gonna get it!   
  
“I’m coming baby!” with a holler, Mutt scuttled a moment on all four like his moniker before getting enough of his bearings to stand up. His call had elicited a cry and thump from upstairs. Prior knowledge telling him the sound originated from Cherry’s room. He didn’t waste a moment running this time. With a snap of his fingers he shortcut right in. He landed in the center of the room facing the bed and the shivering form wrapped in a blanket huddled on the floor.   
  
Mutt crooned at the sight of his little lover arms reaching out to envelope him but stopping short when Cherry wormed away from him flinching. He might not have been the brightest when it came to social cues and was known for acting more on instinct than higher functions but even he knew he had to step back and think first. Rushing always made things worse. 

 

He took stock of the events leading up to this moment and the area around him. The way the Fell’s had vanished without a word before Edge came through only long enough to threaten Mutt’s genitals and lock him in this universe. Cherry was huddling away from him while looking overly flushed with fever and weak. He could see that Cherry was also naked under the blanket and that the entire room smelled delicious like chocolate covered fruits. Heady and decadent.   
  
Cherry was in heat.   
  
Mutt had...Mutt had never heard of Cherry going into heat. They were dating for the most part of a year but they known each other for much longer and never had it come up. Mutt had just assumed that Cherry’s delicate constitution, which was somehow worse the other 1HP Sanses, meant that his body just couldn’t support it. There went that theory out the window.   
  
But then why did Cherry hide from him? It wasn’t Edge that blocked him off despite his mind going down that route. Edge mentioned talking  _ sense _ into Cherry. That meant…   
  
“Cherry baby...are you scared of me knowing you’re in heat?”   
  
“N-NO! That’s not-That’s not why! You didn’t do-do anything wr-ong! I could ne-never be scared of y-you!”   
  
Cherry looked mortified at Mutt’s question and his own outburst. Fresh tears trickling down his cheeks. 

“ I was scared of-” the Sans took a deep shuddering breath before he lowered his protective blanket slowly. Pink dusted bones giving way to candy apple red ecto body. A female ecto body.

Heavy breast ending it tight hardening points. Soft curves and pudge with wide hips where there used to be flat belly. The blanket pooled over tightly clenched thighs hiding what must have obviously been a heat soaked pussy, “...Me”   
  
“I don’t see anything scary Cherry baby. Just someone I love” Mutt murmured. Looking everywhere he could at once. Wishing he hadn’t left his phone. If only he could burn the image of glory before him permanently into his mind. So what if Cherry’s heat made him formed something beyond his usual. What was wrong with that? Mutt knew for a fact Black preferred a female ecto body. (He really hadn’t meant to walk in on THAT)   
  
“You’re not fun-ny! I’m a girl! I have boobs! ” Cherry squealed indignantly. 

 

“Yea you do”  Mutt chuckled leaning forward so he could crawl closer. His eyes read hunger while his stance screamed hunter.    
  
“Mutt do-don’t you da-AH!”    
  
Mutt lifted Cherry up long enough to toss him lightly on to the bed. Laying him out like a virgin sacrifice and Mutt the devil summoned to devour.    
“Ain’t nothing wrong with being soft Cherry. You’re not down there anymore. This is something good. Your body is telling you something”   
  
Cherry scoffed, crossing his arms over his ample chest and his thighs coming together with a muted slap to hide away his core once more. 

Mutt waved around Cherry’s silent indignation. Crawling on the bed to trap the slighter form under him. Humming appreciatively at the extra softness around Cherry’s usually pokey bones.    
  
“You say that because yo-your big and strong! Even my body is-is telling m-me I’m weak and-”   
  
“And cute, and precious, and angry and not thinking straight. I don’t know why you think any less of yourself Cherry Baby but you need to stop. You don’t have to pretend to be this big scary monster. That’s what your body is saying” Mutt said lovingly pulling back so he could gaze into Cherry’s eyelights.    
  
What a sight for sore eyes. The blanket had been abandoned on the floor, so that it no longer covered Cherry’s body.    
  
Mutt leaned to nuzzle his nasal aperture against Cherry’s neck. A deep, pleased rumble starting deep in his chest at Cherry’s submissive mewl and addicting heat scent. Despite Cherry’s mental turmoil his body was arching into Mutt’s warmth. His legs drawing up slowly to imprison the Papyrus in place. Small, shaky hands fisting his sweater pleadingly. 

His little Cherry was always so scared, so shy. He had set such impossible expectations for himself. 

His mind demanding things that he just couldn’t. It seems that after years of struggle his newer healthy body was ready to set itself free. No longer be repressed. Cherry’s body was all but screaming its wants. Throwing him into heat, into a new form, opening itself for their mate. Mutt wanted nothing more then to answer those yearning cries. Turn them into moans of ecstasy.    
  
Claim Cherry as both a man and a woman.    
  
Mutt kissed his way up from scenting Cherry’s neck to his panting mouth. Licking the parted jaw once to seek entrance. Sienna and red meeting in a sensual dance. Tangling first in a mock fight for dominance before Cherry submitted easily. Mutt’s larger tongue filling Cherry’s mouth. Mapping every nook and cranny. Their teeth clicking together repeatedly with each meeting. The sweet delicious taste of his mate filling him.    
  
One of Mutt’s hands coming up to seek one of the plump mounds on Cherry’s chest. Swallowing Cherry’s startled “o-oh!” when he thumbed the pert little bud into full hardness. Rolling Cherry’s pink teat between his fingers before switching to the other breast.    
  
“Amazing. So responsive love.” Mutt released Cherry’s mouth long enough to praise him. Giving him one last peck before traveling down to chest height. Cherry’s back arching wantonly when Mutt’s breath ghosted over his breast. Pushing upward in silent askance. His body once more speaking for him.    
Enveloping one bud into his mouth, Mutt scraped his teeth against the taunt skin teasingly before suckling happily. Mimicking the action that (hopefully) one day babybones would make. Obviously Cherry’s body was stating it was more than ready to accept Mutt’s seed. 

Eventually, in the future.    
  
Using his newly freed hand, Mutt unbuckled his pants. Shaking them down to his knees in relief when his erection was free from its leather confinement. The heavy shaft bobbing in the air leaking profusely. They too joined the neglected blanket on the floor.    
Not releasing his delectable treat, Mutt hunched forward to slide his length against Cherry’s folds.    
  
“Hahn!”   
  
Mutt was damn pleased at Cherry’s high pitched squeal of pleasure. Repeating his motion, making sure the head of his cock tapped the swollen clit nestled toward the top. Cherry’s wetness giving him a liberal coating of lube.    
As much as Mutt wanted to nestle deep into Cherry’s body. The delectable flower was untouched and pure. He would never intentionally harm his delicate lover.    
  
“Ple-please Mutt. More” Cherry begged. The heat syncing his higher functions to his bodies wants. Mutt always treated his body with such veneration. Even when it was quick and nasty, behind Grillby’s or that one time on Edge’s office desk while said skeleton was in the other room unaware.    
But, this felt so much different. Better. Like fire racing through his body, each touch was magnified. Was this new untouched body truly that sensitive or was it the heat? 

 

“I hear you baby. I know exactly what you need” Mutt chuckled. He slithered down the bed to lay between open thighs. The body there yielding under his finger tips. “Shit baby…” Mutt whispered in awe.    
Cherry’s pussy was like a blooming flower. The light glinting off his wet folds. The puffy clit silently begging for Mutt’s teeth. The palpitating hole pleading for his tongue and cock. He swallowed down his drool before diving in.    
  
“HNG!”   
  
The point of his nose digging into Cherry’s pearl. Mutt had pressed his entire face against Cherry’s soft magic. Coiling his tongue as deeply as it would go. The squishy walls parting easily around him. He groaned his appreciation. The dark chocolate taste concentrated here deep inside.    
Rolling his tongue, Mutt scraped his pierced tongue along the rippling walls. The cold barbel heating up quickly in response to the friction and warmth. Mutt might not have been the best with words but he knew how to use his tongue. He sought the soft spongy button upward nestled against Cherry’s walls. Pressing the tapered tip of his tongue against it ruthlessly.    
  
Throwing Cherry headfirst into the first of hopefully many orgasms.    
  
Cherry’s body seized under him. The sharp intake of breath he took forced out soundlessly. The pleasure lighting him up and exploding across his vision. He couldn’t control himself. His legs kicked wildly in Mutt’s restraining grip. Cherry’s hands coming down to claw frantically at Mutt’s scarred skull. His back snapping into a painful arch. His cunt releasing itself all over Mutt’s lower jaw and the bedspread beneath them. Wetting his thighs and butt on the way down.    
  
Mutt helped ease Cherry back down flat. Rubbing soothing circles over the twitching pearl to prolong the pleasure and to distract him. Blanketing Cherry under him Mutt drew him into a kiss before pushing himself swiftly inside. Muffling Cherry’s pained whimpers with his teeth and tongue. He manage to bury half his length in before the pain tightened muscles held him still.    
  
“Sorry baby. Shh, shh it’s ok. Taking me so well your first time. My strong boy” Mutt crooned soothingly. Not once stopping his massaging rounds to Cherry’s bud. His other hand tilting shaking hips at an upward angle to ease the rest of his entry. Fraction by fraction he eased his way in until their hips met.   
  
“Talk to me baby. Does it feel good? Do you like my cock inside your needy cunt?”   
  
“Hurts...hah...but s’good. Love it...so big. Huah...Ple-please Puppy m-move?”   
  
“God damn, Hng, I love when you call me that. Ask me again baby” Mutt pleaded. Despite that his hips were already pulling back slowly. The pleasurable drag of the tightly clasping walls against his cock overwhelming. It took all of his control, not that he had much in the first place bt for Cherry he did, to not hump furiously. His instinct demanding he took everything Cherry had to give and leave the poor small skeleton a shaking, cum covered and stuffed mess.    
  
Maybe in the coming days when the newly bloomed flower was used to repeated intrusion. For now Mutt would worship every little inch under him.   
  
“Please Puppy. You feel so much bi-bigger inside me. Hmmnah hah...Please...please Puppy. Fuck Me!” Cherry whined loudly. His legs once more hitching against Mutt’s pelvis to aid in his inward thrust. Dammit he’s had sex before! Why was he acting like this? He wasn’t some blushing virgin.  Even if his body was.  He wanted Mutt to fucking stop treating him like some delicate piece of glass and   **fuck him** .   
  
Grinning lasciviously, Mutt picked up the pace. Rattling the bed under them with each slowly strengthening push inward. The muscles of Cherry’s pussy finally calming down their stranglehold. Now the greedy cunt was doing its best to welcome him in and keep him there.    
Leaning up Mutt cupped each of the gloriously bouncing breast in his hands. Using them like handles to drag Cherry’s willing body in to his ever increasing pounds.   
His hips slapping against Cherry’s thighs and ass turning the supple flesh a darker hue from the bruising force. The room filled with their combined moans and the wet smacking sounds of their lovemaking.    
  
Mutt didn’t know how much longer he could last. He wanted to fill Cherry up to the brim. Thrust his way through orgasm so he could push his seed further into the rippling passage. Mutt wanted to wring more out of his heat stricken lover. He wanted to make up for all the days they were seperated.    
  
“I’m..gonna cum Mutt please! Please make me cum!” Cherry all but screamed.   
  
“Yes baby. Cum around my cock!” Mutt groaned deeply. Hunching his body forward to wrap his arms completely around Cherry. Flexing his hips in quick jabs into Cherry’s core. His cock twitching in anticipation to release its heavy load.    
  
“M-mutt! Cuuuumming!” Cherry’s ecstatic scream coupled with his exquisite once virginal hole gripping him fiercely.    
  
“Raahah!” Mutt  **roared** . Sinking his false metal fangs beep into Cherry’s collar bone drawing marrow. Grinding his hips to milk himself down to the last drop inside.   
  
They stayed locked like that for a moment longer. Their simultaneous orgasm robbing them of their ability to move. Slowly their bodies relaxed the heat sated for the next few minutes. 

  
Licking the sluggishly bleeding wound apologetically Mutt crooned. Rubbing their cheeks together softly before meeting together in a kiss. Slow and sensual. Their hips rocking softly together now.   
  
Cherry pulled away first. Glancing down demurely, his eye lights flicking up at Mutt before going off to the side. His blush getting brighter each time.    
  
“A-again? I don’t...don’t think I’m convinced yet…”   
  
“Oh I’ll change your mind alright~”

**Author's Note:**

> if you liked it please let me know! Leave a kudos or comment~


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